Many have noted the similarities between Mormonism and Tolkien’s creation stories and others have pointed out Platonic elements in Tolkien. A ring of invisibility is mentioned in the Republic and the first phrase of The Silmarillion, “There was Eru the One,” is especially Platonic since “The One” was the highest deity to the Neoplatonists. Tolkien’s Eru or Iluvatar, though aloof like the One, is rather more like Plato’s demiurge in the Timaeus: the God who plans and oversees the creation.
I’ll address the theme of the gods beneath Iluvatar, the Valar, in my next post, but what I wanted to talk about first were the themes of pre-existence and the fall in The Silmarillion. The rebellion and fall of Melkor (Morgoth) and his Balrogs is clearly like Revelation 10:7-9. The books of Moses and Abraham also have these themes but they also have human pre-existence, a theme not found in Tolkien’s creation narrative. However, Tolkien has a second war in heaven and fall that does suggest a kind of pre-existence: the fall of the Noldor. Iluvatar later creates the Elves (then the Men after that) and places them in Middle Earth where the Valar find them and bring them to Valinor, or heaven. They also capture Morgoth and put him in prison. Yet after Morgoth steals Feanor’s Simlmarils and kills his father Finwe (the king of the Noldar) Feanor gets most of the rest of the Noldor to go with him to chase Morgoth to Middle Earth to try to get the Silmarils back. To do so, the Noldor need the Teleri’s (another Elven house) boats and when the Teleri won’t give them the ships, the Noldor take them by force, or what Tolkien calls “the kin slaying.”
So there’s another war in heaven (Valinor) where another third of the host of heaven (the Noldor are one of three Elven houses) are cast down to earth (or they cast themselves). So whereas the fall of Morgoth and his Balrogs is like the fall of the devil and his angels, the fall of the Noldor is a bit more like pre-existent humans coming to earth from heaven (Morgoth is totally bad, the Noldor and a mix of good and bad).
Plato has pre-mortal beings coming to earth, but no devil. Andrew Michael Ramey in his very popular The Travels of Cyrus (a book with a lot of Mormon-sounding stuff) combined Christian and Platonic themes in a handful of creation myths. In the book, Cyrus, the king of the Persians, visits many of the Middle Eastern and Mediterranean nations to learn about religions and politics. All tell him their cosmogonies about a high god with a wife and son and then some sort of angelic rebellion that caused pre-mortal beings to be cast to earth.
The cosmogony that looks most like Tolkien’s is that of the Jews, told to Cyrus by the priest Eleazar who’s exiled with Daniel in Babylon. Eleazar tells Cyrus of the Jew’s one God who “created diverse orders of intelligences to make them happy.” Eleazar then explains that “Two sorts of spirits lost their happiness by their disloyalty; the one, called cherubim, were of a superior order, and are now infernal spirits; the other, called ischim, were of a less perfect nature; these are the souls which actually inhabit mortal bodies.” Like Tolkien, two groups fell: the superior one became “infernal spirits” and the lesser one became mortals (yes Elves aren’t mortal like Men, but they are still lesser than the Ainur.) Like Tolkien, the rebellion was led by “the chief of the cherubim” (or Ainur, Morgoth) and like Tolkien, the two groups fell for different reasons: “The ichim became too much attached to material objects, and in the enjoyment of created pleasures forgot the supreme beatitude of spirits; the first were too much elated with pride, the second debased themselves by sensuality.” Morgoth falls because of pride, Feanor and the Noldor because of “material objects”: the silmarils.
 Chevalier (Andrew Michael) Ramsay, Travels of Cyrus: To Which is Annexed, A Discourse upon the Theology and Mythology of the Pagans (1727; Albany: Pratt and Doubleday, 1814), 290-92.